Catalyst components for the polymerization of olefins and catalysts therefrom obtained

ABSTRACT

The invention relates to catalyst components, suitable for the preparation of homopolymers and copolymers of ethylene having a broad molecular weight distribution (MWD), which comprise Ti, Mg, Cl, and are characterized by the following properties: surface area, determined by BET method, of lower than 100 m 2 /g, a total porosity, measured by the mercury method, of higher than 0.25 cm 3 /g, a pore radius distribution such that at least 45% of the total porosity is due to pores with radius up to 0.1 μm.

The present invention relates to catalyst components for thepolymerization of olefins CH₂═CHR, wherein R is hydrogen or hydrocarbonradical having 1-12 carbon atoms. In particular, the invention relatesto catalyst components suitable for the preparation of homopolymers andcopolymers of ethylene having a broad molecular weight distribution(MWD), and to the catalysts obtained therefrom.

In particular the present invention relates to a solid catalystcomponent, comprising titanium magnesium and halogen, having sphericalmorphology and particular surface characteristics. Furthermore, thepresent invention relates to a process for preparing ethylenehomopolymers and copolymers characterized by a high melt flow ratio(F/E) value, which is the ratio between the melt index measured with a21.6 Kg load (melt index F) and the melt index measured with a 2.16 Kgload (melt index E), determined at 190° C. according to ASTM D-1238.Said ratio F/E is generally considered as an indication of the width ofmolecular weight distribution. The MWD is a particularly importantcharacteristic for ethylene (co) polymers, in that it affects both therheological behavior and therefore the processability of the melt, andthe final mechanical properties. Polyolefins having a broad MWD,particularly coupled with relatively high average molecular weights, arepreferred in high speed extrusion processing and in blow molding,conditions in which a narrow MWD could cause melt fracture. As aconsequence of this need, different methods have been developed tryingto achieve this property. One of those is the multi-step process basedon the production of different molecular weight polymer fractions insingle stages, sequentially forming macromolecules with different lengthon the catalyst particles.

The control of the molecular weight obtained in each step can be carriedout according to different methods, for example by varying thepolymerization conditions or the catalyst system in each step, or byusing a molecular weight regulator. Regulation with hydrogen is thepreferred method either working in solution or in gas phase.

A problem typically associated with the processes of this type is thatthe different polymerization conditions used in the two steps can leadto the production of not sufficiently homogenous products, especially incases of very broad molecular weight distributions. It is in factdifficult to obtain products having a high F/E ratio, for example higherthan 100, which when subjected to a transformation process, yieldproducts with a low number of unmelt particles (gels). In order to solveor minimize this problem it would be important to have a catalystcapable of producing broad MWD polymers also in a single polymerizationstep. This would allow, in case still broader MWD is desired, the use ofless different polymerization conditions in the sequentialpolymerization process that would finally result in a more homogeneousproduct.

EP-A-119963 discloses catalyst components obtained by the reactionbetween a titanium halide and MgCl₂-based carriers, containing from 1.5to 20% of residual —OH groups, which are obtained by spray-dryingMgCl₂.EtOH solutions. The weight reaction ratio between the titaniumhalide and the MgCl₂ of the carrier has to be kept within the 0.001 to 2range. The catalysts obtained however, are not able to give broad MWDsince the shear sensitivity of the polymers (which is the ratio betweenthe melt indices measured at weight of 20 kg and 2.16 kg at 190° C.) isabout 25 (examples 4-5 and 8-9) although the polymerization processcomprises two polymerization step under different conditions.

Moreover, the catalysts disclosed in this patent application are alwaysused in a suspension polymerization process, while nothing is said aboutgas-phase polymerization. This latter kind of process is nowadays highlypreferred due to both the high qualities of the products obtained and tothe low operative costs involved with it. It would therefore beadvisable to have a catalyst capable to produce broad MWD polymers andhaving at the same time the necessary features allowing its use in thegas-phase polymerization processes.

In EP-A-601525 are disclosed catalysts that, in some cases are able togive ethylene polymers with broad MWD (F/E ratios of 120 are reported).Such catalysts, obtained by a reaction between a Ti compound and aMgCl₂.EtOH adduct which has been subject to both physical and chemicaldealcoholation, are characterized by a total porosity (mercury method)higher than 0.5 cm³/g, a surface area (BET method) lower than 70 m²/g.The pore distribution is also specific; in particular in all thecatalysts specifically disclosed at least 50% of the porosity is due topores with radius higher than 0.125 μ. Although the width of MWD is insome cases of interest, the bulk density of the polymers obtained isrelatively low and this is probably due to non completely regular shapeof the polymer formed which is in turn caused by non-proper behavior ofthe catalyst during polymerization. Hence, it is still very important tohave a solid catalyst component capable of good performances in thegas-phase polymerization process (in particular capable of producinghigh bulk density polymer) and at the same time capable of givingpolymers with a very broad MWD.

It has now surprisingly been found a catalyst component which satisfiesthe above-mentioned needs and that is characterized by comprising Ti,Mg, Cl, and by the following properties:

surface area, determined by BET method, of lower than 100 m²/g,

a total porosity, measured by the mercury method, of higher than 0.25cm³/g

a pore radius distribution such that at least 45% of the total porosityis due to pores with radius up to 0.1 μm.

Preferably the catalyst component of the invention comprises a Ticompound having at least one Ti-halogen bond supported on magnesiumchloride in active form. The catalyst component may also contain groupsdifferent from halogen, in any case in amounts lower than 0.5 mole foreach mole of titanium and preferably lower than 0.3.

The total porosity is generally comprised between 0.35 and 1.2 cm³/g, inparticular between 0.38 and 0.9.

The porosity due to pores with radius up to 1 μm is generally comprisedbetween 0.3 and 1 cm³/g in particular between 0.34 and 0.8. In generalterms the value of the porosity due to pores with radius higher than 1μm is rather limited with respect to the total porosity value. Normallythis value is lower than 25% and in particular lower than 15% of thetotal porosity. The surface area measured by the BET method ispreferably lower than 80 and in particular comprised between 30 and 70m²/g. The porosity measured by the BET method is generally comprisedbetween 0.1 and 0.5, preferably from 0.15 to 0.4 cm³/g.

As mentioned above the catalyst of the invention show a particular poreradius distribution such that at least 45% of the total porosity is dueto pores with radius up to 0.1 μm. Preferably, more than 50%, and inparticular more than 65% of the total porosity is due to pores withradius up to 0.1 μm. If only the porosity due to pores with radius up to1 μm is taken into account, the value of the porosity due to pores withradius up to 0.1 μm is even higher, generally more than 60%, preferablymore than 70% and particularly more than 80%.

This particular pore size distribution is also reflected in the averagepore radius value. In the catalyst component of the invention theaverage pore radius value, for porosity due to pores up to 1 μm, islower than 900, preferably lower than 800 and still more preferablylower than 700. The particles of solid component have substantiallyspherical morphology and average diameter comprised between 5 and 150μm. As particles having substantially spherical morphology, those aremeant wherein the ratio between the greater axis and the smaller axis isequal to or lower than 1.5 and preferably lower than 1.3.

Magnesium chloride in the active form is characterized by X-ray spectrain which the most intense diffraction line which appears in the spectrumof the non active chloride (lattice distanced of 2,56 Å) is diminishedin intensity and is broadened to such an extent that it becomes totallyor partially merged with the reflection line falling at lattice distance(d) of 2.95 Å. When the merging is complete the single broad peakgenerated has the maximum of intensity which is shifted towards angleslower than those of the most intense line.

The components of the invention can also comprise an electron donorcompound (internal donor), selected for example among ethers, esters,amines and ketones. Said compound is necessary when the component isused in the stereoregular (co)polymerization of olefins such aspropylene, 1-butene, 4-methyl-pentene-1. In particular, the internalelectron donor compound can be selected from the alkyl, cycloalkyl andaryl ether and esters of polycarboxylic acids, such as for exampleesters of phthalic and maleic acid, in particular n-butylphthalate,di-isobutylphthalate, di-n-octylphthalate.

Other electron donor compounds advantageously used are the 1,3-diethersof the formula:

wherein R^(I), R^(II), the same or different from each other, are alkyl,cycloalkyl, aryl radicals having 1-18 carbon atoms and R^(III), R^(IV),the same or different from each other, are alkyl radicals having 1-4carbon atoms.

The electron donor compound is generally present in molar ratio withrespect to the magnesium comprised between 1:4 and 1:20.

The preferred titanium compounds have the formula Ti(OR^(v))_(n)X_(y−n),wherein n is a number comprised between 0 and 0.5 inclusive, y is thevalence of titanium, R^(V) is an alkyl, cycloalkyl or aryl radicalhaving 2-8 carbon atoms and X is halogen. In particular R^(V) can ben-butyl, isobutyl, 2-ethylhexyl, n-octyl and phenyl; X is preferablychlorine.

If y is 4, n varies preferably from 0 to 0.02; if y is 3, n variespreferably from 0 to 0.015. A method suitable for the preparation ofspherical components of the invention comprises the following steps:

(a) reacting a compound MgCl₂.mR^(VI)OH, wherein 0.3≦m≦1.7 and R^(VI) isan alkyl, cycloalkyl or aryl radical having 1-12 carbon atoms, with atitanium compound of the formula Ti(OR^(V))_(n)X_(y−n), in which n iscomprised between 0 and 0,5, y is the valence of titanium, X is halogenand R^(V) is an alkyl radical having 2-8 carbon atoms;

(b) reacting the product obtained from (a) with An Al-alkyl compound and

(c) reacting the product obtained from (b) with a titanium compound ofthe formula Ti(OR^(V))_(n)X_(y−n), in which n is comprised between 0 and0,5, y is the valence of titanium, X is halogen and R^(V) is an alkylradical having 2-8 carbon atoms.

The compound MgCl₂.mR^(VI)OH is prepared by thermal dealcoholation ofadducts MgCl₂.pR^(VI)OH, wherein p is equal to or higher than 2 andpreferably ranging from 2.5 to 3.5. It is especially preferred the useof adducts in which R^(VI) is ethyl.

The adducts, in spherical form, are prepared from molten adducts byemulsifying them in liquid hydrocarbon and thereafter solidifying themby quick cooling. Representative methods for the preparation of thesespherical adducts are reported for example in U.S. Pat. No. 4,469,648,U.S. Pat. No. 4,399,054, and WO98/44009. Another suitable method for thespherulization is the spray cooling described for example in U.S. Pat.Nos. 5,100,849 and 4,829,034. As mentioned above the so obtained adductsare subjected to thermal dealcoholation at temperatures comprisedbetween 50 and 150° C. until the alcohol content is reduced to valueslower than 2 and preferably comprised between 0.3 and 1.7 moles per moleof magnesium dichloride.

In the reaction of step (a) the molar ratio Ti/Mg is stoichiometric orhigher; preferably this ratio in higher than 3. Still more preferably alarge excess of titanium compound is used. Preferred titanium compoundsare titanium tetrahalides, in particular TiCl₄. The reaction with the Ticompound can be carried out by suspending the compound MgCl₂.mR^(VI)OHin cold TiCl₄ (generally 0° C.); the mixture is heated up to 80-140° C.and kept at this temperature for 0.5-2 hours. The excess of titaniumcompound is separated at high temperatures by filtration orsedimentation and siphoning. If the titanium compound is a solid, suchas for example TiCl₃, this can be supported on the magnesium halide bydissolving it in the starting molten adduct. In step (b) the productobtained from (a) is then reacted with an aluminum-alkyl compound. Thealuminum alkyl compound is preferably selected from those of formulaR^(VII) _(z)AlX_(3-z) in which R^(VII) is a C₁-C₂₀ hydrocarbon group, zis an integer from 1 to 3 and X is halogen, preferably chlorine.Particularly preferred is the use of the trialkyl aluminum compoundssuch as for example triethylaluminum, triisobutylaluminum,tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum andtris(2,4,4-trimethyl-pentyl)aluminum. Use oftris(2,4,4-trimethyl-pentyl)aluminum is especially preferred. It is alsopossible to use mixtures of trialkylaluminum compounds withalkylaluminum halides, alkylaluminum hydrides or alkylaluminumsesquichlorides, such as AlEt₂Cl and Al₂Et₃Cl₃.

The reaction with the Al-alkyl compound with the product coming from (a)can be carried out in a hydrocarbon solvent at a temperature between−10° C. and 130° C. Preferably the reaction is carried out at atemperature between 40 and 110° C. The molar ratio between the Al-alkylcompound and the product coming from (a) is not particularly critical.Generally the Al-alkyl compound can be used in molar ratios with thealcohol originally contained in the compound (a) from 0.01 to 100.

In the third step, the solid product coming from (b) is further reactedwith a titanium compound of formula Ti(OR^(V))_(n)X_(y−n) in which n,R^(V), X and y have the same meaning given above. The specific titaniumcompound and the reaction conditions can be identical to, or differentfrom, those used in the first step. Normally, the use of the sametitanium compound and the same reaction conditions is preferred.

The catalyst components of the invention form catalysts, for thepolymerization of alpha-olefins CH₂═CHR^(VIII) wherein R^(VIII) ishydrogen or a hydrocarbon radical having 1-12 carbon atoms by reactionwith Al-alkyl compounds. In particular Al-trialkyl compounds, forexample Al-trimethyl, Al-triethyl , Al-tri-n-butyl , Al-triisobutyl arepreferred. The Al/Ti ratio is higher than 1 and is generally comprisedbetween 20 and 800.

In the case of the stereoregular polymerization of α-olefins such as forexample propylene and 1-butene, an electron donor compound (externaldonor) which can be the same or different from the compound used asinternal donor is also generally used in the preparation of thecatalyst. In the case in which the internal donor is an ester of apolycarboxylic acid, in particular a phthalate, the external donor ispreferably selected from the silane compounds containing at least aSi-OR link, having the formula R^(IX) _(4-n)Si(OR^(X))_(n), whereinR^(IX) is an alkyl, cycloalkyl, aryl radical having 1-18 carbon atoms,R^(X) is an alkyl radical having 1-4 carbon atoms and n is a numbercomprised between 1 and 3. Examples of these silanes aremethyl-cyclohexyl-dimethoxysilane, diphenyl-dimethoxysilane,methyl-t-butyl-dimethoxysilane, dicyclopentyldimethoxysilane. It ispossible to advantageously use also the 1,3 diethers having thepreviously described formula. In the case in which the internal donor isone of these diethers, the use of an external donor can be avoided, asthe stereospecificity of the catalyst is already sufficiently high. Thespherical components of the invention and catalysts obtained therefromfind applications in the processes for the preparation of several typesof olefin polymers.

For example the following can be prepared: high density ethylenepolymers (HDPE, having a density higher than 0.940 g/cm³), comprisingethylene homopolymers and copolymers of ethylene with alpha-olefinshaving 3-12 carbon atoms; linear low density polyethylene's (LLDPE,having a density lower than 0.940 g/cm³) and very low density and ultralow density (VLDPE and ULDPE, having a density lower than 0.920 g/cm³,to 0.880 g/cm³ cc) consisting of copolymers of ethylene with one or morealpha-olefins having from 3 to 12 carbon atoms, having a mole content ofunits derived from the ethylene higher than 80%; elastomeric copolymersof ethylene and propylene and elastomeric terpolymers of ethylene andpropylene with smaller proportions of a diene having a content by weightof units derived from the ethylene comprised between about 30 and 70%,isotactic polypropylenes and crystalline copolymers of propylene andethylene and/or other alpha-olefins having a content of units derivedfrom propylene higher than 85% by weight; shock resistant polymers ofpropylene obtained by sequential polymerization of propylene andmixtures of propylene with ethylene, containing up to 30% by weight ofethylene; copolymers of propylene and 1-butene having a number of unitsderived from 1-butene comprised between 10 and 40% by weight. However,as previously indicated they are particularly suited for the preparationof broad MWD polymers and in particular of broad MWD ethylenehomopolymers and copolymers containing up to 20% by moles of higher_(α)-olefins such as propylene, 1-butene, 1 -hexene, 1-octene. Inparticular the catalysts of the invention are able to give ethylenepolymers, in a single polymerization step, with a F/E ratio higher than100 and even higher than 120 that are indicative of exceptionally broadMWD. The F/E ratio can be further increased by operating in twosequential polymerization reactors working under different conditions.

The catalyst of the present invention can be used as such in thepolymerization process by introducing it directly into the reactor.However, it constitutes a preferential embodiment the prepolymerizationof the catalyst. In particular, it is especially preferredpre-polymerizing ethylene or mixtures thereof with one or moreα-olefins, said mixtures containing up to 20% by mole of α-olefin,forming amounts of polymer from about 0.1 g per gram of solid componentup to about 1000 g per gram of solid catalyst component. Thepre-polymerization step can be carried out at temperatures from 0 to 80°C. preferably from 5 to 50° C. in liquid or gas-phase. Thepre-polymerization step can be performed in-line as a part of acontinuos polymerization process or separately in a batch process. Thebatch pre-polymerization of the catalyst of the invention with ethylenein order to produce an amount of polymer ranging from 0.5 to 20 g pergram of catalyst component is particularly preferred.

The main polymerization process in the presence of catalysts obtainedfrom the catalytic components of the invention can be carried outaccording to known techniques either in liquid or gas phase using forexample the known technique of the fluidized bed or under conditionswherein the polymer is mechanically stirred. Preferably the process iscarried out in the gas phase.

Examples of gas-phase processes wherein it is possible to use thespherical components of the invention are described in WO92/21706, U.S.Pat. No. 5,733,987 and WO93/03078. In this processes a pre-contactingstep of the catalyst components, a pre-polymerization step and a gasphase polymerization step in one or more reactors in a series offluidized or mechanically stirred bed are comprised.

Therefore, in the case that the polymerization takes place in gas-phase,the process of the invention is suitably carried out according to thefollowing steps:

(a) contact of the catalyst components in the absence of polymerizableolefin or optionally in the presence of said olefin in amounts notgreater than 20 g per gram of the solid component (A);

(b) pre-polymerization of ethylene or mixtures thereof with one or moreα-olefins, said mixtures containing up to 20% by mole of α-olefin,forming amounts of polymer from about 0.1 g per gram of solid component(A) up to about 1000 g per gram;

(c) gas-phase polymerization of ethylene or mixtures thereof withα-olefins CH₂═CHR, in which R is a hydrocarbon radical having 1-10carbon atoms, in one or more fluidized or mechanically stirred bedreactors using the pre-polymer-catalyst system coming from (b).

As mentioned above, the pre-polymerization step can be carried outseparately in batch. In this case, the pre-polymerized catalyst ispre-contacted according to step (a) with the aluminum alkyl and thendirectly sent to the gas-phase polymerization step (c).

As mentioned above, in order to further broaden the MWD of the product,the process of the invention can be performed in two or more reactorsworking under different conditions and optionally by recycling, at leastpartially, the polymer which is formed in the second reactor to thefirst reactor. As an example the two or more reactors can work withdifferent concentrations of molecular weight regulator or at differentpolymerization temperatures or both. Preferably, the polymerization iscarried out in two or more steps operating with different concentrationsof molecular weight regulator. In particular, when the catalysts of theinvention are used in this kind of process they are able to giveethylene polymers having exceptionally broad MWD while, at the sametime, maintaining a good homogeneity. Once used in the production offilms indeed, the polymers showed a very good processability while thefilms obtained showed a very low number of gels.

The following examples are given in order to further describe and not tolimit the present invention.

The properties are determined according to the following methods:

Porosity and surface area with nitrogen: are determined according to theB.E.T. method (apparatus used SORPTOMATIC 1900 by Carlo Erba).

Porosity and surface area with mercury:

The measure is carried out using a “Porosimeter 2000 series” by CarloErba. The porosity is determined by absorption of mercury underpressure. For this determination use is made of a calibrated dilatometer(diameter 3 mm) CD₃ (Carlo Erba) connected to a reservoir of mercury andto a high-vacuum pump (1-10⁻² mbar). A weighed amount of sample isplaced in the dilatometer. The apparatus is then placed under highvacuum (<0.1 mm Hg) and is maintained in these conditions for 20minutes. The dilatometer is then connected to the mercury reservoir andthe mercury is allowed to flow slowly into it until it reaches the levelmarked on the dilatometer at a height of 10 cm. The valve that connectsthe dilatometer to the vacuum pump is closed and then the mercurypressure is gradually increased with nitrogen up to 140 kg/cm². Underthe effect of the pressure, the mercury enters the pores and the levelgoes down according to the porosity of the material.

The porosity (cm³/g), both total and that due to pores up to 1 μm, thepore distribution curve, and the average pore size are directlycalculated from the integral pore distribution curve which is functionof the volume reduction of the mercury and applied pressure values (allthese data are provided and elaborated by the porosimeter associatedcomputer which is equipped with a “MILESTONE 200/2.04” program by C.Erba.

MIE flow index: ASTM-D 1238 MIF flow index: ASTM-D 1238 Bulk density:DIN-53194 Fraction soluble in xylene: determined at 25° C. Effectivedensity: ASTM-D 792

Determination of gel number: 1 Kg of polymer is pelletized by a BanderaTR15 pelletizer for 1 hour keeping the temperature at 230° C. in all thesections with the screw rotating at 50 rpm. The first 300 grams ofmaterial are discarded while the remaining is introduced in aPlasticizers MKII film extruder with a 3000 mesh/cm² filter in which theprofile temperature was 260-260-260-270-270° C. and the screw rotationspeed was 30 rpm. The determination of the number of gels per m² iscarried out by visually detecting the number of gels having size higherthan 0.2 mm on a piece of the extruded film (30×4 cm size) which isprojected by a projector, on the wall-chart with a magnificated scale.The counting is made on 3 different pieces of the same film and a finalnumber is given by the expression No=A/S where No is the number of gelsper m², A is the number of gels counted on 3 film pieces and S is theoverall surface in m² of the 3 films pieces examined.

EXAMPLES PREPARATION OF THE SPHERICAL SUPPORT (ADDUCT MgCl₂/EtOH)

A magnesium chloride and alcohol adduct was prepared following themethod described in example 2 of U.S. Pat. No. 4,399,054, but working at2000 RPM instead of 10000 RPM. The adduct containing about 3 mols ofalcohol had an average size of about 70 μm with a dispersion range ofabout 45-100 μm.

Example 1

Preparation of the Solid Component

The spherical support, prepared according to the general methodunderwent a thermal treatment, under N₂ stream, over a temperature rangeof 50-150° C. until spherical particles having a residual alcoholcontent of about 25% (0.69 mole of alcohol for each MgCl₂ mole) wereobtained. Into a 72 l steel reactor provided with stirrer, 44 liters ofTiCl₄ at 0° C. and whilst stirring 2200 g of the support wereintroduced. The whole was heated to 130° C. over 60 minutes and theseconditions were maintained for a further 60 minutes. The stirring wasinterrupted and after 30 minutes the liquid phase was separated from thesettled solid. Thereafter 4 washings with anhydrous hexane (about 22liters) were performed two of which were carried out at 80° C. and twoat room temperature.

Then, after the addiction of 31 liters of anhydrous hexane, 11 liters ofa solution of tris(2,4,4-trimethyl-pentyl)aluminum (Tioa) in hexane (100g/l) were introduced at room temperature into the reactor and stirredfor 30 minutes. The liquid phase was separated from the settled solidthat was washed with 22 liters of hexane and with 22 liters of heptane(twice for each other) at room temperature.

Thereafter a further treatment with 44 liters of TiCl₄ was performed inthe same condition with respect to the first one, and after 4 washingswith anhydrous hexane, 2200 g of the spherical solid component wereobtained. After drying under vacuum at about 50° C., the solid showedthe following characteristics:

Total titanium 4.6% (by weight) Ti^(m) 0.6% (by weight) M 0.11% (byweight) Mg 17.0% (by weight) Cl 73.4% (by weight) OEt 0.3% (by weight)porosity (B.E.T.) 0.153 cm³/g surface area (B.E.T.) 50.6 m²/g totalporosity (Hg) 0.692 cm³/g, 70% of which was due to pores with radius upto 0.1 _(μ)m. Porosity due to pores with radius up to 1 _(μ)m: 0.552Average pore radius: 0.0827 surface area (Hg) 31.5 m²/g

Ethylene Polymerization (HDPE)

Into a 10 liters stainless steel autoclave, degassed under N₂ stream at70° C., 4 liters of anhydrous hexane, 0.15 g of spherical component and1.5 g of triisobutylaluminum (Tiba) were introduced. The whole wasstirred, heated to 75° C. and thereafter 4 bar of H₂ and 7 bar ofethylene were fed. The polymerization lasted 3 hours during whichethylene was fed to keep the pressure constant. 2120 g of polymer wasobtained having the following characteristics:

MIE 0.12 g/10 min MIF/MIE 127.5 effective density 0.960 g/cm³ bulkdensity 0.355 g/cm³ morphology spherical

1 kg of the so obtained polymer has been subject to the measurement ofthe gel number according to the procedure previously described and theresult was 730 gel/m².

Example 2

Preparation of the Solid Component

The spherical support, prepared according to the general methodunderwent a thermal treatment, under N₂ stream, over a temperature rangeof 50-150° C. until spherical particles having a residual alcoholcontent of about 15% (0.37 mole of alcohol for each MgCl₂ mole) wereobtained. Into a 2 l glass reactor provided with stirrer, 0.5 liters ofTiCl₄ at 0° C. and whilst stirring 50 g of the support were introduced.The whole was heated to 60° C. over 15 minutes and these conditions weremaintained for a further 60 minutes. The stirring was interrupted andafter 10 minutes the liquid phase was separated from the settled solid.Thereafter 3 washings with anhydrous hexane (about 0.5 liters) wereperformed at room temperature. Then, after the addiction of 1 liter ofanhydrous heptane, 0.24 liters of a solution oftris(2,4,4-trimethyl-pentyl)aluminum (Tioa) in hexane (250 g/l) wereintroduced at room temperature into the reactor. The reactor was heatedat 50° C. and the solution was stirred for 60 minutes. The liquid phasewas separated from the settled solid that was washed twice with 0.5liters of hexane at room temperature.

Into the reactor, 0.5 liters of TiCl₄ and 0.5 liters of heptane wereintroduced, the solution was heated at 100° C. and after 30 minutes andthe liquid phase was separated from the solid component.

Then, 1 liter of TiCl₄ was introduced into the glass reactor. The wholewas heated to 130° C. over 30 minutes and these conditions weremaintained for a further 60 minutes. The stirring was interrupted andafter 10 minutes the liquid phase was separated from the settled solid.Thereafter 3 washings with anhydrous hexane at 60° C. and 3 washings atroom temperature were performed. After drying under vacuum at about 50°C., the solid showed the following characteristics:

Total titanium 3.3% (by weight) Ti^(m) 1.0% (by weight) Al 0.4% (byweight) Mg 20.2% (by weight) Cl 72.7% (by weight) OEt 1.2% (by weight)porosity (B.E.T.) 0.298 cm³/g, surface area (B.E.T.) 2.2 m²/g totalporosity (Hg) 0.684 cm³/g, 80% of which was due to pores with radius upto 0.1 _(μ)m. Porosity due to pores with radius up to 1 _(μ)m: 0.631Average pore radius: 0.0558 surface area (Hg) 60.7 m²/g

Ethylene Polymerization (HDPE)

Into a 4 liters stainless steel autoclave, degassed under N₂ stream at70° C., 1600 cc of anhydrous hexane, 0.02 g of spherical component and0.3 g of triisobutylaluminum (Tiba) were introduced. The whole wasstirred, heated to 75° C. and thereafter 4 bar of H₂ and 7 bar ofethylene were fed. The polymerization lasted 2 hours during whichethylene was fed to keep the pressure constant. 225 g of polymer wasobtained having the following characteristics:

MIE 0.14 g/10 min MIF/MIE 137.0 effective density 0.960 g/cm³ bulkdensity 0.40 g/cm³ morphology spherical

Example 3

Into a 1 l glass reactor provided with stirrer, 0.8 liters of TiCl₄ at0° C. and whilst stirring 40 g of the support prepared as explained intothe example 3, were introduced. The whole was heated to 130° C. over 15minutes and these conditions were maintained for a further 30 minutes.The stirring was interrupted and after 10 minutes the liquid phase wasseparated from the settled solid. Thereafter 3 washings with anhydroushexane (about 0.8 liters) were performed at room temperature.

Then, after the addiction of 0.3 liter of anhydrous hexane, 37 cc of asolution of triethylauminum (Tea) in hexane (100 g/l) were introduced atroom temperature into the reactor and stirred for 30 minutes. The liquidphase was separated from the settled solid that was washed three timeswith 0.4 liters of heptane at room temperature.

Into the reactor, 0.8 liters of TiCl₄ were introduced, the solution washeated at 130° C. and after 30 minutes and the liquid phase wasseparated from the solid component. Thereafter 3 washings with anhydroushexane at 60° C. and 3 washings at room temperature were performed.After drying under vacuum at about 50° C., the solid showed thefollowing characteristics:

Total titanium 5.9% (by weight) Ti^(m) 2.7% (by weight) Al 0.52% (byweight) Mg 18.8% (by weight) Cl 71.2% (by weight) OEt 0.6% (by weight)porosity (B.E.T.) 0.239 cm³/g, surface area (B.E.T.) 43.1 m²/g totalporosity (Hg) 0.402 cm³/g, 85% of which was due to pores with radius upto 0.1 _(μ)m. Porosity due to pores with radius up to 1 _(μ)m: 0.359Average pore radius: 0.0369 _(μ)m surface area (Hg) 54.0 m²g

Ethylene Polymerization (HDPE)

0.02 g of the spherical component were used in ethylene polymerizationunder the same conditions described in example 2.

180 g of polymer were obtained having the following characteristics:

MIE 0.16 g/10 min MIF/MIE 152.0 effective density 0.960 g/cm³ bulkdensity 0.414 g/cm³ morphology spherical

Comparison Example 4

Preparation of the Solid Component

The spherical support, prepared according to the general methodunderwent a thermal treatment, under N₂ stream, over a temperature rangeof 50-150° C. until spherical particles having a residual alcoholcontent of about 35% (1.1 mole of alcohol for each MgCl₂ mole) wereobtained. 2700 g of this support were introduced into a 60-lautoclavetogether with 38 l of anhydrous hexane. Under stirring and at roomtemperature 11.6 liters of hexane solution containing 100 g/l of AlEt₃were fed over 60 minutes.

The temperature was raised to 50° C. over 60 minutes and was maintainedat that temperature for a further 30 minutes whilst stirring. The liquidphase was removed by filtration; the treatment with AlEt₃ was repeatedtwice again under the same conditions. The spherical product obtainedwas washed three times with anhydrous hexane and dried at 50° C. undervacuum. The thus obtained support showed the following characteristics:

porosity (Hg) 1.2 g/cm³ surface area (Hg) 18. m²/g OEt residual 5.% (byweight) Al residual 3.4% (by weight) Mg 20.1% (by weight)

Into a 72 l steel reactor provided with stirrer 40 liters of TiCl₄ wereintroduced; at room temperature and whilst stirring 1900 g of the abovedescribed support were introduced. The whole was heated to 100° C. over60 minutes and these conditions were maintained for a further 60minutes. The stirring was interrupted and after 30 minutes the liquidphase was separated from the settled solid. Two further treatments werecarried out under the same conditions with the only difference that inthe first of these treatment it was carried out at 120° C. and in thesecond at 135° C. Thereafter 7 washings with anhydrous hexane (about 19liters) were carried out three of which were carried out at 60° C. and 4at room temperature. 2400 g of component in spherical form were obtainedwhich, after drying under vacuum at about 50° C., showed the followingcharacteristics:

Total titanium 8.2% (by weight) Ti^(m) 6.1% (by weight) Al 1.4% (byweight) Mg 16% (by weight) Cl 67.8% (by weight) OEt 0.3% (by weight)porosity (B.E.T.) 0.155 cm³/g, surface area (B.E.T.) 32.9 m²/g totalporosity (Hg) 0.534 cm³/g, 40% of which was due to pores with radius upto 0.1 _(μ)m. Porosity due to pores with radius up to 1 _(μ)m: 0.475Average pore radius: 0.2294 _(μ)m surface area (Hg) 40 m²/g

Ethylene Polymerization (HDPE)

Into a 10 liters stainless steel autoclave, degassed under N₂ stream at70° C., 4 liters of anhydrous hexane, 0.02 g of spherical component and1.2 g of triisobutylaluminum (Tiba) were introduced. The whole wasstirred, heated to 75° C. and thereafter 4 bar of H₂ and 7 bar ofethylene were fed. The polymerization lasted 3 hours during whichethylene was fed to keep the.pressure constant. 1920 g of polymer wasobtained having the following characteristics:

MIE 0.11 g/10 min MIF/MIE 105 effective density 0.960 g/cm³ bulk density0.315 g/cm³

1 kg of the so obtained polymer has been subject to the measurement ofthe gel number according to the procedure previously described and theresult was 9000 gel/M².

Example 5

Preparation of HDPE by a two Step Sequential Polymerization Process

Into a 4 liters stainless steel autoclave, degassed under N₂ stream at70° C., 2 liters of propane, 0.067 g of the spherical component preparedaccording to the procedure of Example 1 and 0.7 g of triisobutylaluminum(Tiba) were introduced. The whole was stirred, heated to 75° C. andthereafter 2.5 bar of H₂ and 7 bar of ethylene were fed. Thepolymerization lasted 30 minutes during which 160 g of polyethylene wereproduced. After this period the autoclave was degassed and then a secondstep was performed with the same catalyst and under the same conditionswith the only difference that the hydrogen pressure was 7 bar. Thissecond step lasted 7 hours and gave 640 g of polyethylene.

The total 800 g therefore obtained had the following characteristics:

MIE 0.21 g/10 min MIF/MIE 212 effective density 0.960 g/cm³ bulk density0.41 g/cm³ Gel number 500/m²

What is claimed is:
 1. Catalyst components for the polymerization ofolefins CH₂═CHR^(VIII), wherein R^(VIII) is hydrogen or an hydrocarbonradical having 1-12 carbon atoms, comprising Ti, Mg and Cl, andcharacterized by the following properties: surface area, determined byBET method, of lower than 100 m²/g, a total porosity, measured by themercury method, of higher than 0.25 cm³/g and, a pore radiusdistribution such that at least 45% of the total porosity, as measuredby the mercury method, is due to pores with radius up to 0.1 μm. 2.Catalyst components according to claim 1 in which the catalyst componentcomprises a Ti compound having at least one Ti-halogen bond supported onmagnesium chloride in active form.
 3. Catalyst components according toclaim 1 containing groups different from halogen, in an amount lowerthan 0.3 mole for each mole of titanium.
 4. Catalyst componentsaccording to claim 1 in which the total porosity is between 0.35 and 1.2cm³/g.
 5. Catalyst components according to claim 4 in which the totalporosity is between 0.38 and 0.9 cm³/g.
 6. Catalyst components accordingto claim 1 in which the porosity due to pores with radius up to 1 μm isbetween 0.3 and 1 cm³/g.
 7. Catalyst components according to claim 6 inwhich the porosity due to pores with radius up to 1 μm is between 0.34and 0.8.
 8. Catalyst components according to claim 4 in which the valueof the porosity due to pores with radius higher than 1 μm is lower than25% with respect to the total porosity.
 9. Catalyst components accordingto claim 8 in which the value of the porosity due to pores with radiushigher than 1 μm is lower than 15% with respect to the total porosity.10. Catalyst components according to claim 1 in which the surface areameasured by the B.E.T. method is lower than 80 m²/g.
 11. Catalystcomponents according to claim 10 in which the surface area is between 30and 70 m²/g.
 12. Catalyst components according to claim 1 in which theporosity measured by the BET method is comprised between 0.1 and 0.5cm³/g.
 13. Catalyst components according to claim 12 in which theporosity is from 0.15 to 0.4 cm³/g.
 14. Catalyst components according toclaim 1 in which more than 50% of the total porosity is due to poreswith radius up to 0.1 μm.
 15. Catalyst components according to claim 1in which more than 65% of the total porosity is due to pores with radiusup to 0.1 μm.
 16. Catalyst components according to claim 1 in which anaverage pore radius value, for porosity due to pores up to 1 μm, islower than 0.09 μm.
 17. Catalyst components according to claim 16 inwhich the average pore radius value, for porosity due to pores up to 1μm, is lower than 0.08 μm.
 18. Catalyst components according to claim 17in which the average pore radius value, for porosity due to pores up to1 μm, is lower than 0.07 μm.
 19. Catalyst components according to claim1 in which the titanium compound has the formula Ti(OR^(V))_(n)X_(y−n),wherein n is a number comprised between 0 and 0.5 inclusive, y is thevalence of titanium, R^(V) is an alkyl, cycloalkyl or aryl radicalhaving 2-8 carbon atoms and X is chlorine.
 20. Catalyst componentsaccording to claim 19 in which y is 3 or 4, and n is
 0. 21. A processfor the preparation of the catalyst components of claim 1 comprising thefollowing steps: (a) reacting a compound MgCl₂.mR^(VI)OH, wherein0.3≦m≦1.7 and R^(VI) is an alkyl, cycloalkyl or aryl radical having 1-12carbon atoms, with a titanium compound of the formulaTi(OR^(V))_(n)X_(y−n), in which n is comprised between 0 and 0.5, y isthe valence of titanium, X is halogen and R^(V) is an alkyl radicalhaving 2-8 carbon atoms; (b) reacting the product obtained from (a) withan Al-alkyl compound and (c) reacting the product obtained from (b) witha titanium compound of the formula Ti(OR^(V))_(n)X_(y−n), in which n iscomprised between 0 and 0.5, y is the valence of titanium, X is halogenand R^(V) is an alkyl radical having 2-8 carbon atoms.
 22. The processaccording to claim 21 in which the compound MgCl₂.mR^(VI)OH is preparedby thermal dealcoholation of adducts MgCl₂.pR^(VI)OH, wherein p is anumber higher than
 2. 23. The process according to claim 21 in which thetitanium compound used in steps (a) and (c) is TiCl₄.
 24. The processaccording to claim 21 in which R^(VI) is ethyl.
 25. The processaccording to claim 21 in which the aluminum alkyl compound of step (b)is selected from those of formula R_(z)AlX_(3-z) in which R is a C₁-C₂₀hydrocarbon group, z is an integer ranging from 1 to 3 and X ischlorine.
 26. The process according to claim 25 in which the aluminumalkyl compound is a trialkyl aluminum compound selected from the groupconsisting of triethylaluminum, triisobutylaluminum,tri-n-butylaluminum, tri-n-hexylaluminum and tri-n-octylaluminum. 27.The process according to claim 26 in which the aluminum alkyl compoundis tri-n-octylaluminum.
 28. Catalysts for the polymerization of olefinscomprising the product of the reaction between an aluminum alkylcompound and a catalyst component according to claim
 1. 29. Process forthe polymerization of olefins CH₂═CHR^(VIII), wherein R^(III) ishydrogen or an hydrocarbon radical having 1-12 carbon atoms, carried outin the presence of a catalyst according to claim
 28. 30. Process for thepreparation of broad molecular weight distribution ethylene polymershaving a F/E ratio higher than 100 characterized in that it is carriedout in the presence of a catalyst according to claim
 28. 31. The processaccording to claim 30 in which the F/E ratio is higher than
 120. 32. Theprocess according to claim 30 characterized by the fact that it iscarried out in more than one step working under different polymerizationconditions.
 33. Pre-polymerized catalyst for the polymerization ofolefins obtained by pre-polymerizing ethylene or mixtures thereofcontaining one or more α-olefins, with a catalyst according to claim 28and thereby forming amounts of polymer from 0.1 up to 1000 g per gram ofsolid catalyst component.
 34. The process for the polymerization ofolefins CH₂═CHR^(VIII), wherein R^(VIII) is hydrogen or an hydrocarbonradical having 1-12 carbon atoms, carried out in the presence of acatalyst according to claim
 33. 35. The process for the preparation ofbroad molecular weight distribution ethylene polymers having a F/E ratiohigher than 100 characterized in that it is carried out in the presenceof a catalyst according to claim 33.